You should already have your track and arrow car.
We are going to split the Blender Screen.'
Place your mouse right under the title bar. It will
turn into two arrows. 
Right Click.
Click Split Areas.
Move your mouse down to the work area. You should have
a line there.
Left Click.
You should now have two windows.
Put your mouse in the window on the right.
Press Shift F6.
Right Click the curve you selected. The curve should turn pink.
Go to frame 1.
Hold Ctrl and Left Click.
A white dot will appear.
Add some more white dots along the path. My path ends
at 250 frames so I have white dots all the way to 250.
If your curve drops down like this
your roller coaster will go
backwards. Press Ctrl Z to undo any mistakes.
Press the Tab KEY.
Now you have handles that you can move around.
